The sequential application of these operators demands that the MPS be
brought to canonical form (i.e., orthonormalizing the indices) after
every time step \(\delta \) .[1]} Such a procedure involves
\(O(poly(N)poly(D))\)  steps, where \(D\)  is the maximum internal bond
dimension of the MPS. In the absence of truncation, \(D\)  grows
exponentially with both the system size and the evolution time and the
computational cost of this procedure quickly becomes intractable for
large systems and long times.
